The behavior of polystyrene in injection molding is improved with a broad molecular weight distribution in the polymer. The presence of low molecular weight species improves the rate of melt flow at low temperatures, whereas high molecular weight constituents are desirable to obtain adequate strength and to avoid excessive brittleness. It is known, in U.S. Pat. No. 4,137,388, for instance, that broad molecular weight distribution in polystyrene can be obtained by two stage suspension polymerization in which some of the styrene and a low temperature initiator are used in a first stage and additional styrene and high temperature initiator are reacted in a second stage.